It is common practice to move articles from place to place within a large warehouse by use of tow trucks. It has recently been found advisable for various reasons to make these tow trucks remotely controlled. Such a system is shown in the patent of Swartz U.S. Pat. No. 3,988,991, wherein the tow truck is shown as guided along the path defined by a groove or track in the floor. At decision-making points, such as at a switch point, a scanner is buried in the floor to read a pattern code mounted on the tow truck to determine its destination and to take suitable action. Because the scanning equipment is located in the floor, the equipment of this type is constantly being rendered less than effective by the presence of dust. Not only does the dust settle on the optical elements of the scanner, but it is often necessary for the reading beam of energy to operate through a dusty atmosphere. Since the beam must pass from the scanner to the retro-reflective signal device or target on the tow truck and then return to the scanner, the length of its path is double the distance, so that the effect of the dust on the strength of the signal is very great. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a vehicle control system which operates effectively despite the presence of dust in the air.
Another object of this invention is the provision of a vehicle control system, including retro-reflective control equipment, in which the proper operation of the equipment can be observed without interferring with the operation of the tow truck.
A further object of the present invention is the provision of a vehicle control system, using a plurality of scanners, in which the operation of the individual scanners as well as a main control unit into which they feed can be verified externally of the equipment.
It is another object of the instant invention to provided a vehicle control equipment in which the alignment of individual scanners is set in the factory, so that not only does field installation require no alignment, but the replacement of scanners in the field is facilitated.
A still further object of the invention is the provision of a vehicle control system which is simple in construction, which is easily manufactured, and which is capable of a long life of useful service with a minimum of maintenance.
It is a further object of the invention to provide a retro-reflective control unit which is unlikely to be rendered inoperative by vibration.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.